The present invention relates to a valve unit which is suitable when miniaturization and weight reduction thereof are required to be mounted to a robot arm and it is required to have a monitor function of an output pressure, like a valve having a fluid pressure control mechanism for driving a gun cylinder for spot welding.
It is general to control a clamp pressure in a gun cylinder for spot welding by a pressure control apparatus, and to output the pressure through a valve. In such a case, general-purpose parts are used as the pressure control apparatus, the valve and a pressure sensor, and they are individually disposed and connected to each other by piping. Therefore, piping installation is required therebetween, and when the entire structure is complicated due to the piping, weight thereof is increased, and in order to mount the valve to a robot arm or the like, miniaturization, weight reduction, simplification of the structure, simplification of the piping installation of the structure and the like are desired. This is required when the pressure control apparatus, the valve and the like are to be mounted to the robot arm but in generally, miniaturization is always required for plant and equipment.
Further, when elements such as the pressure control apparatus, the valve and the pressure sensor are individually installed as described above, when completion or the like of pressure setting by the pressure control apparatus is to be monitored, the wiring and piping therefor become complicated, and devices for monitoring are confusedly disposed. Further, when the elements such as the pressure control apparatus, the valve and the pressure sensor are connected to each other by piping, pressure loss in the connection piping becomes great, a capacity of a pressure air sealing portion in the piping is increased. Thus, there is a problem that the pressure setting precision is lowered, and responsivity is also lowered.
It is a technical object of the present invention to provide a valve unit having a fluid pressure control mechanism which is mounted to a robot arm and used, in which means for monitoring a state in which the setting of an output pressure or a pressure is completed can be incorporated easily and compactly.
It is another technical object of the invention to provide a valve unit in which a need of piping between the pressure control apparatus, the valve and the pressure sensor is eliminated and as a result, miniaturization, weight reduction, simplification of the structure, simplification of the piping installation of the structure and the like are simplified so that the monitor means for the output pressure and the like can be incorporated compactly.
It is another technical object of the invention to provide a valve unit capable of monitoring an output pressure in which increase in pressure loss caused by the piping and increase in capacity of a pressure air sealing portion are suppressed, pressure setting precision and responsivity are enhanced.
It is another technical object of the invention to provide a valve unit capable of monitoring the output pressure in which a general-purpose base-mount type valve which is mounted on a base is utilized as it is, and a pressure control apparatus can be sandwiched between the base and the valve.
To achieve the above object, according to the present invention, there is provided a valve unit capable of monitoring an output pressure, comprising a base having a plurality of holes including a supply hole, a valve having a plurality of ports including a supply port, and a pressure control apparatus interposed between these base and valve for controlling a pressure of air supplied from the supply hole to the supply port, the base, the valve and the pressure control apparatus being integrally combined with each other.
The pressure control apparatus in this valve unit comprises a pressure control section which controls and outputs a pressure of air supplied from the supply hole of the base such that the pressure becomes equal to a set pressure applied from outside by an electric signal; a booster section for outputting a large amount of air to the supply port of the valve when an output pressure is controlled by air from the pressure control section; a first pressure sensor for detecting a pressure of the air output from the pressure control section to the booster section; a second pressure sensor for detecting a pressure of air output from the booster section to the valve; and a signal control section having a function to compare the pressure detected by the first pressure sensor and the set pressure, and when these pressures become equal to each other, to maintain the pressure control section in that control state, and having a function to compare the pressure detected by the second pressure sensor and the set pressure, and when these pressures become equal to each other, to output a monitor signal indicative of completion of pressure setting.
The pressure control apparatus may include a lamp which is lit when the pressure setting is completed.
According to concrete structure of the present invention, the pressure control section of the pressure control apparatus includes a diaphragm driving valve for controlling the booster section in accordance with the electric signal for setting a pressure, and a supply valve and an exhaust valve both for driving the diaphragm driving valve, the diaphragm driving valve includes first and second diaphragm chambers formed on opposite sides of a diaphragm, an air supply valve member which is opened when a pressure in the first diaphragm chamber is higher than a pressure in the second diaphragm chamber, and an exhaust valve member which is opened when the former pressure is lower than the latter pressure, the first diaphragm chamber is in communication with the supply hole of the vase through the supply valve, the exhaust valve is in communication with outside through the exhaust valve, the second diaphragm chamber is in direct communication with the booster section and is in communication with the supply hole of the base through the air supply valve member and is also in communication with outside through the exhaust valve member, the signal control section has a function to open and close the supply valve and the exhaust valve in accordance with a difference between the set pressure and a pressure detected by the first pressure sensor.
According to another concrete structure of the present invention, the booster section of the pressure control apparatus includes a slidable piston, a first piston chamber and a second piston chamber formed on opposite sides of the piston, a rod extending from the piston, and a valve chamber opposed to a tip end of the rod, a control pressure output passage which is in communication with the supply port of the valve, a supply passage which is in communication with the supply hole of the base and an exhaust passage which is opened into outside are in communication with the valve chamber, a supply valve seat is formed between the output passage and the supply passage, an exhaust valve seat is formed between the output passage and the exhaust passage, a supply valve member and an exhaust valve member which are driven by the rod to open and close a valve seat thereof are provided, the first piston chamber is in communication with the pressure control section, and the second piston chamber is in communication with the valve chamber.
According to further another concrete structure of the invention, the pressure control apparatus includes a flow path forming portion, the flow path forming portion includes the supply hole of the base, the supply passage connecting a pressure control section and a booster section, and the control pressure output passage connected the booster section and the valve, and includes a plurality of vent holes which bring other holes on the base except the supply hole and other ports of the valve except the supply port in communication with each other.
According to the present invention having such structures, in the valve unit having the fluid pressure control mechanism, means for monitoring a state in which the setting of an output pressure or a pressure is completed can easily and compactly be incorporated in the valve unit having a fluid pressure control mechanism, a need of piping between the pressure control apparatus and the valve or the pressure sensor is eliminated by sandwiching the pressure control apparatus between the base and the valve, it is possible to achieve miniaturization, weight reduction, simplification of the entire structure, and simplification of the piping installation. Further, increase in pressure loss which may be caused by piping installation or increase in capacity of compressed air sealing portion are suppressed by omitting the piping and with this, it is possible to enhance the pressure setting precision and responsivity.